46. Secretion enzyme breakdown and reabsorption in the mouth. Control of the secretion. Swallowing – phases and control

saliva

Salivary glands are responsible for saliva secretion through ducts emptying into the oral

cavity; the major pairs are parotid (serous), submandibular (mixed), and sublingual glands

(mixed).

COMPOSITION:

-99.5% water and 0.5% solutes

à Salivary alpha-amylase (amylolytic enzyme) à digestion of starch in the mouth

à Lingual lipase (lipolytic enzyme) à digestion of TAG

à Mucus lubricates the food for easier swallowing

à Lysozyme enzyme à destroy bacteria to protect mucous membrane from infection and

the teeth from decay

• Saliva is around 1L/24hrs

• Basic pH - around 7 (6.8)

Just to know:

Resting saliva is low in enzymes and slightly acidic, stimulates saliva is high in enzymes and

alkaline

CONTROL OF SECRETION

• Secretion of saliva is controlled by the nervous system:

• Parasympathetic stimulation (facial & glossopharyngeal nerves):

  • Increases saliva production by acinar cells

  • Increases blood flow to glands

  • Contracts myoepithelium to expel saliva faster

  • Saliva is dilute, low in enzymes, rich in salts

• Sympathetic stimulation:

  • Releases noradrenaline binding to alpha & beta receptors

  • Decreases saliva production by acinar cells

  • Increases protein secretion

  • Decreases blood flow to glands

  • Saliva is dense, enzyme-rich, poor in salts

• During dehydration:

  • Salivary glands stop secretion to conserve water

  • Causes dry mouth and sensation of thirst

you already know regulation and phases of swallowing

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